MALARIA

Malaria

Malaria

Malaria parasites have been with us since the beginning of time, and fossils of mosquitoes up to thirty million years old show that malaria's vector has existed for just as long. The parasites causing malaria are highly specific, with man as the only host and mosquitoes as the only vector. Every year, 300,000,000 people are affected by malaria, and while less than one percent of these people die, there are still an estimated 1,500,000 deaths per year. While Malaria was one of the first infectious diseases to be treated successfully with a drug, scientist are still looking for a cure or at least a vaccination today (Cann, 1996). Though many people are aware that malaria is a disease, they are unaware that it is life threatening, kills over a million people each year, and is a very elusive target for anti-malarial drugs (Treatment of Malaria, 1996).

Being a very specific disease, malaria is caused by only four protozoal parasites: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. Not only is the disease specific, but the parasites are too, with only 60 of 380 species of female Anopheles mosquitoes as vectors. With the exception of Plasmodia Malariae which may affect other primates, all parasites of malaria have only one host, Homo sapiens. Because some mosquitoes contain substances toxic to Plasmodium in their cells, not all species of mosquitoes are vectors of Plasmodium. Although very specific, malaria still causes disruption of over three hundred million people worldwide each year (Cann, 1996).

The life cycle of the parasite causing malaria exists between two organisms, humans and the Anopheles mosquito. When a female mosquito bites a human, she injects an anticoagulant saliva which keeps the human bleeding and ensures an even flowing meal for her. When the vector injects her saliva into the human, it also injects ten percent of her sporozoite load. Once in the bloodstream, the Plasmodium travel to the liver and reproduce by asexual reproduction. These liver cells then burst releasing the parasites back into the bloodstream where they then enter red blood cells. Here, the Plasmodium feed on hemoglobin and reproduce again by asexual reproduction. Afterwards, the red blood cells burst and release the parasites. Some of the parasites released from red blood cells may be able to replicate by sexual reproduction. When the host has been bitten by a mosquito again, infected blood inters the mosquito. Here, sexual forms of the parasite develop in the stomach of the Anopheles mosquito completing the parasites life cycle (Herman, 1996).

People infected malaria have several symptoms including fever, chills, headaches, weakness, and an enlarged spleen (Herman, 1996). The amount of time for symptoms to appear differs depending on the form of the parasite. Those infected with Plasmodium falciparum experience symptoms after about twenty-four hours, those infected with Plasmodium vivax and Plasmodium ovale produce symptoms after a forty-eight hour interval, and after seventy-two hours Plasmodium malariae begin causing fever and chills (Cann, 1996).

Most malaria cases seem to cluster in the tropical climate areas extending into the ...